Light-emitting diode and method of producing the same

ABSTRACT

A light-emitting diode with which the LED chip will not be destroyed comprises an LED chip  40  mounted on plate-shaped wiring means  60  inside a light-emitting diode. Wiring means  60  comprises conductive paths  61  and  62  that electrically lead to a pair of opposing surfaces. The top surface is used for mounting the LED chip. Part of the conductive paths  61, 62  are connected electrically to LED chip  40,  extending from the position where the LED is mounted to leads  21  and  22,  to which they are connected by soldering. LED chip  40  is supported by being held inside concave part  23  in one lead  21  at this time.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention pertains to a light-emitting diodecomprising LED chips, that is, light-emitting diode chips.

[0003] 2. Description of the Prior Art

[0004] Examples of this type of light-emitting diode are disclosed inJapanese Kokai Patent No. Hei 11(1999)-346,007 and Japanese Patent No.2,982,553. The light-emitting diode disclosed in the former has LEDchips and a pair of electrostatic protective elements in the concavepart (or cup) made in one lead of a pair of leads. One electrode of apair of electrodes of the LED chips is electrically connected to thelead holding the LED chip through the electrostatic protective elements,and the other electrode is connected to the electrostatic protectiveelement and also electrically connected to another lead by wire bondingtechnique.

[0005] On the other hand, according to the latter document, a single LEDchip is electrically connected such that the chip bridges a pair ofleads. This type of mounting method is called flip-chip mounting. Theadvantage of flip-chip mounting is that it can prevent opening of wiresfor connection in temperature cycles, which can occur in the structureshown in the former document.

[0006] The structure of flip-chip mounting disclosed in the abovedocuments shows resin, which can conventionally seal the diode chipsfrom outside. In this case, because of relatively large thermalexpansion coefficient of the resin, stress is generated in the LED chipwhen force is applied to the pair of leads from the resin due to thermalexpansion and contraction, and the chip may be destroyed in the worstscenario. Consequently, the object of the present invention is topresent a light-emitting diode with which the LED chip will not bedestroyed.

SUMMARY OF THE INVENTION

[0007] The present invention provides a light-emitting diode, having anLED chip electrically connected to a pair of leads characterized in thatsaid LED chip is mounted on a plate-shaped wiring means and connected tosaid pair of leads by said wiring means.

[0008] Preferably, said flexible wiring means is a single means.

[0009] Preferably, at least one of said pair of leads includes a supportpart for supporting a portion of said wiring means on which said LEDchip is mounted.

[0010] Preferably, said support part is concave such that said supportpart can surround said LED chip.

[0011] Preferably, said wiring means comprises a 3-dimensional wiringmeans.

[0012] Preferably, said wiring means comprises a circuit board ortape-like electrical wire.

[0013] Preferably, an electronic element is further mounted on saidwiring means, said element being selected from a group of a protectiveelement and a sensor to monitor heat or light.

[0014] Preferably, said wiring means includes a pair of chip mountingelectrodes mutually separated by only a relatively short distance and apair of lead connecting electrodes mutually separated by a relativelylong distance.

[0015] Preferably, said wiring means has flexibility.

[0016] Furthermore, the present invention provides a method of producinga light-emitting diode, comprising the steps of mounting at least oneLED chip having a pair of electrodes on a plate-shaped wiring means withat least a pair of electrical paths, and mounting said wiring means on apair of leads and thereby electrically connecting said pair ofelectrodes to said pair of leads by said pair of electrical paths.

[0017] Preferably, said step of mounting at least one LED chip comprisesa step of mounting several LED chips on a single substrate, where saidsubstrate includes s plurality of wiring means.

[0018] Preferably, said method further comprises a step of cutting saidsubstrate to have specific dimensions such that said plurality of wiringmeans are separated after said step of mounting several LED chips.

[0019] Preferably, said method further comprises a step of testing saidLED chips using said wiring means after said step of separating saidplurality of wiring means.

[0020] According to the light-emitting diode of the present invention,the LED chip is mounted on a plate-shaped wiring means. The wiring meanscomprises a pair of conductive paths electrically connecting between apair of opposing surfaces. One of the surfaces is for mounting an LEDchip. The pair of conductive paths is electrically connected to the LEDchip and extends from the LED-mounting section to the lead-connectingsections. The lead-connecting sections are connected to thecorresponding lead by soldering. At least one of the lead-connectingsections overlap the LED chip mounted on the wiring means, and as aresult, the LED is stabilized by being supported by the lead. It ispreferred that the plate-shaped wiring means have at least someflexibility, but it can also be rigid.

[0021] Moreover, according to the method of producing semiconductorelements of the present invention, the LED chip is firstly mounted on asubstrate including a single wiring means or a set of plurality ofwiring means. In the latter case, the substrate is later cut into theappropriate dimensions and the plurality of wiring means can beseparated. Then the required tests are performed on the LED chip mountedon the wiring means. When the tests have been completed, the wiringmeans is connected to the corresponding lead by a conventional methodsuch as soldering, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a figure showing a light-emitting diode showing thefirst embodiment of the present invention. (a) is an oblique view closeto the end of the lead and (b) is a cross section view of the entirediode structure.

[0023]FIG. 2 is a cross section view showing a part close to the end ofthe lead of the light-emitting diode showing the second embodiment wherethe plate-shaped wiring means has been modified.

[0024]FIG. 3 is a cross section view showing a part close to the end ofthe lead of the light-emitting diode showing the third embodiment wherethe plate-shaped wiring means has been modified.

[0025]FIG. 4 is a cross section showing a part close to the end of thelead of the light-emitting diode showing the fourth embodiment whereinthe plate-shaped wiring means has been modified.

[0026]FIG. 5 is a diagram of an example of the method of producing asubstrate assembly comprising a plate-shaped wiring means that can beused for each embodiment in FIGS. 1 through 4.

DEFINITION OF SYMBOLS

[0027]21, 22; 121, 122; 221, 222; 321, 322; 421, 422 Leads

[0028]40; 140; 240; 340; 440 LED chip

[0029]60; 160; 260; 360; 460 Wiring means

[0030]61, 62; 161, 162, 163, 164; 261, 262, 263, 264; 361, 362, 363,364; 461, 462 Electrode wires

[0031]380 Electrostatic protective element

[0032]23; 123; 223; 323; 423 Concave part (support part)

DESCRIPTION OF THE INVENTION

[0033] Preferred embodiments of the light-emitting diode and method ofproducing the same of the present invention will now be described indetail with reference to the figures.

[0034]FIG. 1 is a figure showing the light-emitting diode that is thefirst embodiment of the present invention. (a) is an oblique view nearthe end of the lead and (b) is a cross section of the entire diodestructure.

[0035] As illustrated, light-emitting diode 10 has pair of leads 21 and22 and resin 70 sealing the chip and portions of the leads. One lead 21has a concave part 23 in its end for holding LED chip 40. The obliquesurface on the inside of concave part 23 acts to reflect light emittedfrom LED chip 40. As shown in the figure, LED chip 40 inside concavepart 23 rides on the end of plate-shaped wiring means 60. The twoelectrodes of LED chip 40 are connected through plate-shaped wiringmeans 60 to leads 21 and 22, respectively. This structure is describedin further detail hereinafter:

[0036] As is clear from FIG. 1(b), plate-shaped wiring means 60comprises a base plate 63 and part of wirings 61 and 62. The base plate63 is curved in at least two positions, has a middle part 65 extendingobliquely, and extends so that it bridges leads 21 and 22. As shown inthe figure, when plate-shaped wiring means 60 rides inside of concavepart 23, oblique middle part 65 extends such that a gap with anappropriate distance from the inner surface of concave part 23 is madealong the inner surfaces. The wirings 61 and 62 can be formed byprinting, etc., along the surface of base plate 63. Both wirings formthe conductive paths of LED chip 40 and leads 21 and 22.

[0037] The wirings 61 and 62 are connected to the electrodes of LED chip40 at the base of LED chip 40 by solder pastes 91 and 92. In particular,the wiring 61 is folded over the base plate 63 at one end where LED chip40 is mounted. The wiring 61 extends to overlap only with the positionof LED chip 40 (at least the position of solder pastes 91 and 92, whichis where LED chip 40 and plate-shaped wiring means 60 are joined) and isconnected to lead 21 by solder paste 51. On the other hand, the wiring62 extends to the end on the other side and is folded over the base ofbase plate 63 and connected to lead 22 by solder paste 52. It should benoted that LED chip 40 is joined to base 26 of concave part 23 by solderpaste 51 and is thereby anchored inside the concave part and stabilized.

[0038] Plate-shaped wiring means 60 can be a flexible means, such as aflexible circuit board or ribbon-like wire, or it can be rigid to acertain extent, such as something like a resin plate with a metal coreas a base plate 63. The wirings 61 and 62 must be formed on the baseplate 63, and therefore, at least the surface thereof should be madefrom an insulating material.

[0039]FIGS. 2 and 3 show cross sections around the ends of the leads ofthe light-emitting diodes that are the second and third embodiments ofother wiring means.

[0040] According to FIG. 2, LED chip 140 is also connected to leads 121and 122 through plate-shaped wiring means 160. 100 is added to thereference numerals for the constituents that have the same function oradvantage as in FIG. 1 in principal for the explanation. A differencebetween the embodiments shown in FIG. 2 and FIG. 1 is an arrangement ofwirings. That is, plate-shaped wiring means 160 has wirings 161 and 162and 163 and 164 that are separated at the top and bottom of the baseplate and the wirings 161 and 163 and the wirings 162 and 164 areelectrically connected through through holes 171 and 172. The wirings161 and 162 are connected to LED chip 140, while wirings 163 and 164 areconnected to leads 121 and 122, respectively.

[0041] Moreover, according to FIG. 3, LED chip 240 has plate-shapedwiring means 260 with the same structure as wiring means 160. 200 isadded to the reference numerals of the constituents that have the samestructure as in FIG. 1. The point of difference between FIG. 3 and FIG.2 is how LED chip 240 is mounted. The electrodes of LED chip 140 to beconnected to the wiring means 160 by solder pastes 191 and 192 arelocated at the bottom side of the chip 140 as shown in FIG. 2, while inthe embodiment shown in FIG. 3 the electrodes are found at the sides ofLED chip 240, and LED chip 240 and plate-shaped wiring means 260 areelectrically connected by solders 291 and 292. The rest of the structureis similar to the example in FIG. 1 or FIG. 2 and therefore, furtherdescription is omitted.

[0042]FIG. 4 is a cross section showing the structure close to the endsof the leads of the light-emitting diode that is the fourth embodimentincluding another modification of the present invention. The basicstructure is similar to FIG. 1 and therefore, 300 is added to thereference numerals for constituents having the same function andadvantage in principal.

[0043] According to this embodiment, electrostatic protective element380, such as a diode, etc., is further mounted on plate-shaped wiringmeans 360. Electrostatic protective means 380 is shown in FIG. 4 whichis connected to wiring 362, but a protective circuit such as thatdisclosed in Japanese Kokai Patent No. Sho 62(1987)-299092 can be madeon the plate-shaped wiring means 260 so that LED chip 340 is protectedfrom static electricity. Furthermore, it can be seen electrostaticprotective element 380 is placed on lead 322. Thus, electrostaticelement 380 is stabilized by being mechanically supported by lead 322.Other kinds of electronic elements can be mounted on the plate-shapedwiring means such as a sensor to monitor light emitted from LED or heatgenerated from the LED chip. Such elements can be mounted together withor instead of the protective elements shown in the embodiment.

[0044]FIG. 5 is a diagram of an example of a method of producing asubstrate assembly comprising a plate-shaped wiring means that can beused in each of the embodiments shown in FIGS. 1 through 4. Theplate-shaped wiring means in FIG. 5 is represented by reference numeral460, but it can be plate-shaped wiring means 60, 160, 260, or 360 inother embodiments.

[0045] Substantially flat substrate or plate 400 is prepared for thefirst process of production shown in FIG. 5(a). As previously described,substrate 400 can have flexibility (be flexible) or it can be rigid to acertain extent. Several blocks are formed in substrate 400 and theappropriate wires (or electrodes) 461 and 462 are formed inside eachindividual block by printing technology or conventional board-formingtechnology. A perforation, etc., can be formed at interface 450 of eachblock.

[0046] According to the second process of production shown in FIG. 5(b),LED chip 440 is mounted at an appropriate place for each block onsubstrate 400. LED chip 440 is close to the end of each block in theillustrated example. Then, as shown in FIG. 5(c), substrate 400 isdivided into each block by cutting, etc., and individual substrateassemblies 500, that is, plate-shaped means 460 on which LED chips areindividually mounted, are produced.

[0047] The operation of each chip-plate assembly 500 having plate-shapedwiring means 460 as the main part can be tested before it is connectedto the leads 421, 422. If the chip-plate assembly 500 with LED chip 440that does not have required performance by performing tests withdetector 600, the chip can be removed. Plate-shaped wiring means 460 canbe easily handled and consequently, testing can be more efficientlyperformed. Moreover, defective parts can be found before assembly andtherefore, the present invention can reduce waste of materials such asfor making the LED product more efficiently than conventional methodswhere testing is performed after assembly is completed. The chip-plateassembly 500, on which test has been finished, is connected to the leads421 and 422 and electrical connection is thereby completed.

[0048] The light-emitting diode and method of producing the same of thepresent invention has been explained in detail, but they are strictlyexamples and do not limit the present invention. Various changes can beapplied by persons skilled in the art.

What is claimed is:
 1. A light-emitting diode, having an LED chipelectrically connected to a pair of leads characterized in that: saidLED chip is mounted on a plate-shaped wiring means and connected to saidpair of leads by said wiring means.
 2. A light-emitting diode accordingto claim 1, further characterized in that said wiring means is a singlemeans.
 3. A light-emitting diode according to claim 2, furthercharacterized in that: at least one of said pair of leads includes asupport part for supporting a portion of said wiring means on which saidLED chip is mounted.
 4. A light-emitting diode according to claim 3,further characterized in that: said support part is concave such thatsaid support part can surround said LED chip.
 5. A light-emitting diodeaccording to claim 1, further characterized in that: said wiring meanscomprises a 3-dimensional wiring means.
 6. A light-emitting diodeaccording to claim 1, further characterized in that: said wiring meanscomprises a circuit board or tape-like electrical wire.
 7. Alight-emitting diode according to claim 1, further characterized inthat: an electronic element is further mounted on said wiring means,said element being selected from a group of a protective element and asensor to monitor heat or light.
 8. A light-emitting diode according toclaim 2, further characterized in that: said wiring means includes apair of chip mounting electrodes mutually separated by only a relativelyshort distance and a pair of lead connecting electrodes mutuallyseparated by a relatively long distance.
 9. A light-emitting diodeaccording to claim 1, further characterized in that: said wiring meanshas flexibility.
 10. A method of producing a light-emitting diode,comprising the steps of: mounting at least one LED chip having a pair ofelectrodes on a plate-shaped wiring means with at least a pair ofelectrical paths, and mounting said wiring means on a pair of leads andthereby electrically connecting said pair of electrodes to said pair ofleads by said pair of electrical paths.
 11. A method of producing alight-emitting diode according to claim 10, further characterized inthat: said step of mounting at least one LED chip comprises a step ofmounting several LED chips on a single substrate, where said substrateincludes s plurality of wiring means.
 12. A method of producing alight-emitting diode according to claim 11, further characterized inthat: said method further comprises a step of cutting said substrate tohave specific dimensions such that said plurality of wiring means areseparated after said step of mounting several LED chips.
 13. A method ofproducing a light-emitting diode according to claim 12, furthercharacterized in that: said method further comprises a step of testingsaid LED chips using said wiring means after said step of separatingsaid plurality of wiring means.
 14. The light-emitting diode in claim10, further characterized in that: said wiring means is flexible.